dreded

First post so go easy on me... I'm very new to prestashop as well. I want to integrate prestashop with an external application. The "customers" will be maintained though prestashop. I don't need to change anything in relation to prestashop, but I would like to synchronize the customer database maintained by prestashop with an external database. So the operations like registrations updating addresses that are local to prestashop, would be followed by a one line ajax call to the external application. All I would really like to know is where are the calls in the PS files, so that I can place my calls immediately after. I have started looking in the authController, but I haven't managed to locate it just yet. Is that the file I should be looking into? I'm using PS 1.5